1. Field of the Invention
The present invention relates generally to prefabricated shower modules and, more particularly, a method for improving manufacturability of a pre-molded leak-proof shower module having surfaces for receiving shower tile, marble or stone thereon.
2. Description of the Prior Art
Most tile-covered shower enclosures are created using complicated construction methods. For example, using conventional techniques, a skilled installer frames out the area to be enclosed using two-by-four wooden or aluminum studs to create a frame and curb. Felt or tar paper is then laid over a subfloor area enclosed within the newly formed frame. A flexible, leak-proof liner is installed on top of the felt or tar paper and attached to the frame. Next, the installer attaches dry wall boards to the framing studs, creating shower sidewalls. A hole is cut in the liner to allow for a drain, and a layer of mortar is applied to the shower sidewalls and curb and allowed to cure. Additional mortar is applied on top of the leak-proof liner and hand-shaped to form a shower floor which slopes toward the drain such that water from the shower flows toward the drain. After the mortar has cured, shower tile is applied to the sidewalls and floor to create the finished enclosure.
The process of creating the enclosed shower is time-consuming and requires a certain degree of skill in order to maintain the proper pitch and uniformity in shaping the floor. Irregularities in the pitch of the floor can cause water from the shower not to drain properly or make tiling the shower enclosure difficult. The liners are also susceptible to punctures or leaks and may be difficult for the installer to properly form square corners at the intersection of the shower sidewalls and floor. Additionally, the mortar layer used to create the floor is necessarily thick in order to form a sloped surface, therefore the time required for the floor to cure before applying tile may be quite long (e.g., greater than 24 hours).
In recent years, the process of shower installation has been vastly improved by the introduction of prefabricated shower base modules used for forming the floor. Use of the prefabricated modules significantly decreases the amount of time and skill required to construct a tile-covered shower enclosure, as well as providing more of a consistent and reliable flooring surface upon which to tile. These modules are pre-constructed molded units having a sloping floor, an integrated drain, curb, sidewalls, and a horizontal surface on the top of each sidewall for mounting drywall such that the drywall is substantially flush to the module sidewalls. Installation of the module involves securing a section of drain pipe to the drain, applying adhesive and sealing material to the subfloor where the module will rest, and seating the module on the subfloor. Tile can then be applied directly to the shower walls and module without the need for first applying mortar.
However, these prefabricated shower modules contain weaknesses in the design which add cost to the final product. For instance, certain modules are manufactured using plastics-forming processes that inject molten polymeric resins into molds. After filling the mold with the resin, the module must cool (e.g., solidify) before being removed. If the module is removed before it is completely solid, bowing may occur as the module hardens. However, the mold or “tool” for creating each unit can be quite expensive, thus a manufacturer generally limits the number of tools for producing each module. Therefore, the number of modules manufactured in a given amount of time depends on the amount of time required for one module to sufficiently cool enough to be removed from the mold.
Because the mold is needed to create other modules, the manufacturer is pressed to find ways to decrease the required cooling time. This problem is exacerbated by non-uniform thicknesses of the plastic material throughout the module. Cooling rates for thick areas of the module are slower than for thinner areas. Thus, if the module is removed from the mold before it is completely cooled, areas of the modules having different thicknesses cool at different rates, resulting in bowing across the surface of the floor As a result, severely bowed modules must be discarded, increasing the unit cost for other modules. Additionally, slightly bowed modules present potential field problems (i) by impacting uniform tile adhesion on the upper surface of the floor of the shower module, (ii) by preventing the lower surface of the floor of the shower module from sitting flush on the subfloor, and (iii) by changing the pitch of the upper floor of the shower module, which causes puddling or ponding of water on the upper floor of the shower module rather than properly pitched draining. Further, uneven cooling along the drain aperture may result in a misshapen aperture, thereby (i) preventing the installer from acquiring (or hampering his/her ability to acquire) a water-tight seal around the drain fixture, and (ii) interfering with the insertion of the drain fixture into the drain aperture. Uneven cooling along the drain assembly (i) may prevent a proper connection (e.g., a water-tight connection) between the drain assembly and the shower module, (ii) may warp the drain aperture at the top of the drain assembly, thereby interfering with the insertion of the drain top into the top of drain assembly, and (iii) may warp the drain aperture in the bottom of the drain assembly, thereby interfering with the connection of the drain assembly to the plumbing line.
Further, each size module requires a specific mold, thus the manufacturer is forced to limit the selection of available modules to a few standard sizes. Because the curb may be integrated into the shower module, both the positioning of the curb, as well as the overall dimensions of the module are set by a single tool. The design options for a customer (e.g., an architect, a designer, a contractor, an installer, or homeowner) desiring to implement a prefabricated shower module are therefore limited to a few set arrangements.
Additionally, features such as shower benches or ledges must still be constructed by hand, or added in a piece-meal fashion, thereby compromising the leak-proof integrity of the prefabricated shower module.
Therefore, a need exists for, among other things, a method for improving manufacturability of a pre-molded leak-proof shower module having surfaces for receiving shower tile, marble or stone thereon, and the associated shower module, to overcome the shortcomings of the prior art.